Pressure-operated layered electrical switch and switch array

ABSTRACT

1. AN ELECTRICAL SWITCH WHICH IS CLOSED BY THE APPLICATION OF PRESSURE AGAINST AN AREA OF THE SWITCH AND IS OPENED WHEN THE PRESSURE IS REMOVED COMPRISING A. AN ELECTRICALLY NONCONDUCTIVE BASE; B. A FIRST ELECTRICALLY CONDUCTIVE LAYER POSITIONED AGAINST SUCH BASE; C. A NONCONDUCTIVE SEPARATOR MEANS PLACED AGAINST THE SIDE OF THE CONDUCTIVE LAYER OPPOSITE THE BASE, SAID SEPARATOR MEANS HAVING AN OPENING THEREIN; D. A SECOND ELECTRICALLY CONDUCTIVE LAYER PLACED AGAINST THE SIDE OF THE SEPARATOR MEANS OPPOSITE THE FIRST CONDUCTIVE LAYER; E. A LAYER OF NONCONDUCTIVE NONCOMPRESSIBLE MATERIAL PLACED AGAINST THE SIDE OF THE SECOND ELECTRICALLY CONDUCTIVE LAYER OPPOSITE THE NONCONDUCTIVE LAYER MEANS,   SAID NONCOMPRESSIBLE LAYER HAVING AN ELONGATED OPENING POSITIONED ADJACENT THE OPENING IN THE SEPARATOR MEANS; AND F. A PRESSURE-RESPONSIVE DEFLECTABLE PORTION OF THE NONCOMPRESSIBLE LAYER POSITIONED ADJACENT THE OPENING CAPABLE OF BEING DEFLECTED DOWN INTO SAID OPENING WHEREBY THE APPLICATION OF PRESSURE TRANSMITTED TO AND AGAINST THE PRESSURE-RESPONSIVE DEFLECTABLE PORTION CAUSES SAID PORTION TO MOVE A PORTION OF THE SECOND CONDUCTIVE LAYER AGAINST THE FIRST CONDUCTIVE LAYER TO CLOSE THE SWITCH.

XR REZBBS Much 18, 1975 c. E. BRAUE Re. `28,365

PRESSURE-OPERATED LAYERED ELEGTRICAL SWITCH AND SWITCH ARRAY 2Sheets-Shout 1 Original Filed April 30, 1970 FIG. 1

Much 18, 191s C, E, BRAUE RO. zaes i PRESSURE-OPERATED LAYEREDELECTRICAL SWITCH AND SWITCH V.ARRAY Original Filed April 3G, 1970 2Sheets-Sheet l FIG. 4

United States Patent Re. 28,365 Reissued Mar. I8, 1975 28,365PRESSURE-OPERATED LAYERED ELECTRICAL SWITCH AND SWITCH ARRAY Charles E.Braue, Bronx, N.Y., assigner to Data Appliance Corporation Original No.3,617,666, dated Nov. 2, 1971, Ser. No.

33,367, Apr. 30, 1970. Application for reissue June 27, 1973, Ser. No.374,091

Int. Cl. H01h 43/08 U.S. Cl. 20G-86 29 Claims Matter enclosed ln heavybrackets [J appears in the original patent but forms no part of thisreissue specilication; matter printed in italics indicates theaddition., made by reissue.

ABSTRACT OF THE DISCLOSURE A pressure-operated electrical switch unithaving a layered construction including a substantially planar surfaceto which pressure is applied to close the switch. The removal of thepressure opens the switch. The switch includes a layer having at leastone elongated opening in it which permits portions of the layer to bedeflected into an opening in an adjacent layer to move one electricallyconductive layer to complete the electrical circuit. An array of theswitches may be used for supplying signals created by the pressure of awriting instrument.

BACKGROUND OF THE INVENTION Electrical switches which are actuated byexerting pressure against their surfaces to complete a circuit and whichopen the circuit when pressure is removed have been used for variousapplications including mat switches to operate door-opening devices.Other prior disclosures include pressure-sensitive switches arranged ingrids and intended to be used with embossed card readers andhandwriting` recording devices; for example, the device shown in U.S.Pat. No. 3,308,253 issued to International Business Machines Corporationon Mar. 7, i967. The switch disclosed in this patent functions through aelastomer diaphragm which is deformed by the application of a force tothereby move a conductive material which is secured to the underside ofthe diaphragm into contact with a second conductive material. Uponremoving the force, the elastomer diaphragm restores itself to itsoriginal position.

Switches of this design have the disadvantage of being over sensitive toa force applied over a larger area since elastomer materials are readilydeformed. When a plurality of these switches are used in a multipleswitch unit for recording handwriting or other marks made using awriting instrument, such as a pen, pencil or stylus, the varying degreesof pressure applied by portions of the hand including, in particular,the knuckle of the little finger, as it rests on and moves over theswitches will cause certain of switches to be unintentionally closed.The problem of inadvertent closing of switches has not heretofore beensolved. On the other hand, the closing of each switch must easily bedone so as not to tire an operator who may be called on to close manyswitches at one sitting.

A pressure-sensitive switch which will operate reliably for extendedperiods of time to close upon the application of a selected pressurewhich is within the range of normal writing instrument pressures andwhich will not in the published literature nor available to industry.

SUMMARY OF THE INVENTION Broadly, the present invention is a switchdevice operable by the selective application of pressure to an area ofthe device which causes a sheet having deectable portions created by anelongated opening in the sheet. The deflection of these portions againsta first conductive layer moves that layer against a second layer whichis normally spaced from the first layer thus completing an electricalcircuit. When the pressure is released, the deflected portions move backto their inactive position allowing the normally spaced-apart layers tomove apart and open the circuit.

It is a feature of the device that it is capable of providing signalsfor recording through the normal use of a pencil or stylus as thepressure-applying means. Preferably a checkotf form or other piece ofpaper is placed over the switch which paper delineates the areas towhich pressure may be applied through use of a writing instrument. Whenan intentional and su'lcient pressure has been applied to an area, theclosing of the switch may cause an audible sound to be heard to notifythe operator that the switch closed.

It is also a feature that the detlective action of the nonconductivelayer cooperates advantageously with conductive layers made of flexiblefabric having a conductive oxide coating.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings, FIG. l is a planview, partially broken away, showing a plurality of switches in a gridarrangement; FIG. 2 is a sectional view taken along line 2-2 of FIG. lwith a pencil point touching but not applying pressure to the surface;and FIG. 3 is a sectional view, similar to FIG. 2, showing the switchhaving pressure applied to it.

FIG. 3a is an enlarged partial view of FIG. 2 showing conductive fabriclayers moved into engagement; FIG. 4 is an enlarged plan view of theswitch and FIG. 5 is a further embodiment showing a three-element switchusing three layers of conductive fabric; FIG. 6 is an enlarged partialview of FIG. 5 showing conductive fabric layers moved into engagement.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIGS. 1, 2 and 3,switch unit 1 is constructed of a plurality of layers including abaseplate 2 made of electrically nonconductive material, such as plasticor paper board, a lower layer of fabric 3, a separator sheet 4, a secondlayer of fabric 5, an electrically nonconductive substantiallynoncompressible deilector layer 6 and finally a pressure-transmittingprotective sheet 7. These layers may be held together by adhering,clamping or otherwise securing their edges together to provide a sealpreventing the water, dirt or bacteria from entering between the layers.The interior surfaces of the layers are not attached to allow therelative movement necessary to the proper functioning of each switch. Asheet of paper 8 including portions indicating where marks should bemade is placed on top of the unit and is marked with a pencil point 9 orother writing instrument.

Individual switches 11 are formed by the portions of the layers in andaround circular opening l2 of separator Sheet 4. Each switch 1l issimilarly constructed, with fabric layers 3 and S each having,alternatively, an electrically conductive row 13 and a nonconductive row14.

The conductive rows 13 of layer 3 run perpendicular to rows 13 of layer5. The fabric may be made in any con vcntional manner, such as byweaving, matting or knitting. [t is required that at least thenonconductive rows of the fabric be manufactured from the nonconductivefibers which may be made of any fiber, natural or synthetic, such asnylon, polyesters or silk. The conductive rows are made by coating thoseportions with a thin coating of an electrically conductive metal, suchas silver or chromium. Alloys of the metals may also be used. A coatingwhich is effectively continuous over the fabric portion having athickness of about l 10i to 40x10-6 inches is operable with thethickness of 2x10E to 6 l03 inches being preferred. The coating is thinenough and adhered to, or absorbed in the bers to prevent the fibers orsignificant groups of bers from becoming attached one to another toreduce the flexibility of the fabric. The coating must also extend overportions of contiguous bers, including those at the surfaces and in theinterior, to assure a complete electrical engagement of fibersthroughout the fabric portions. Fibers having denier in the range of 0.5to 10 are preferred.

The coatings may be applied using the method disclosed in the U.S. Pats.Nos. 2,511,472, 2,867,552, 2,896,570, 2,897,091, 3,014,818, 3,043,796,and 3,862,783. These patents include methods for coating the fibersbefore the fabric is made and provide a coating that will not wear,crack or flake during use in the switch arrangement herein disclosed.

The entire section of fabric to be used in a switch arrangement may becoated and thereafter the coating in the row areas desired to benonconductive removed by using a suitable solvent. Alternatively, thestrips of fabric may be manufactured having conductive properties andhaving nonconductive properties and the rows thereafter attachedtogether by sewing adhesives or other suitable means. Preferably themetal coatings used will be resistant to corrosion in the environmentherein disclosed.

Fabric layers 3 and 5 have the properties of flexibility and corrosionresistance and, in particular, layer 5 has the ability to repeatedlyrespond to movement of the deector layer 6 and to thereafter restoreitself to a position in which the layer is in a plane. Layers 3 and 5may also be made of other materials, such as flexible plastic sheetswith portions of conductive material adhered to areas of the sheet toprovide rows 13 and 14; however, the material should be able to berepeatedly deflected into openings 12 and thereafter be able to restoreitself as the pressure is released.

Row 13 is positioned to pass over or under an opening 12 so that aspressure is applied to deection layer 6 portions of the layer 6 deflectinto openings 12, as generally shown in FIG. 4, to urge a portion of anupper row 13 against a portion of lower row 13.

Referring in particular to FIGS. 3 and 4, it is seen that theapplication of pressure by pencil point 9 causes lip portions 19 and 19alocated adjacent each opening l2 of layer 6 to be deected downward in acantilever action. As portions 19 and 19a move downward edges 17 and 17aof the lips move further apart. The action of the slit adjacent lipportions 19 and 19a create a contact area 18 of fabric-to-fabricengagement when the pencil point 9 is urged downward. Each lip 19 and19a assumes a generally semicircular shape as it bends downward. Whenthe pressure is removed the lips move back into the plane of theremainder of layer 6. Where the application of pressure by the pencilpoint is not in the central area of opening l2 the configurations ofmovement of the lips and size and shape of area 18 will both vary;however, application of sucient pressure applied anywhere within thecircumference of circular opening 12 will cause two areas of rows 13 toengage to close the switch. Even when pressure is not equally applied toeach lip, the ability of each lip to move independently permits afabric-to-fabric engagement.

The cantilever action of lip portions 19 and 19a also assists inpreventing a permanent set or dimple being placed in protective sheet 7.The force of the pencil point defiects sheet 7 into an arcuate shape(FIG. 3) as lips 19 and 19a move in the manner herein described thusreducing the pressure on sheet 7 and preventing dimpling of the sheet.

Protective sheet 7 is preferably made of Mylar brand polyester film,sold by E. I. du Pont de Nemours Company. Other types of material may beused if they are sufficiently resilient to resist the formation ofdimples in the surface. Separator layer 4 and nonconductive deflectionlayer 6 may also be made of Mylar or other material. With respect toseparator layer 4 it is necessary that the material be suicientlyincompressible to prevent lips 19 and 19a from compressing the portionof layer 4 near opening 12 and interfering with the bending action ofdetlection lips 19 and 19a. Deflection in the manner shown in FIGS. 2and 3 without substantial deformation layer 4 is required so that normalpencil point pressure will close the switch while a lesser pressure willnot activate the switch. Rows 13 are connected through terminals 21 ofleads 22 to connect the electrical circuits with switches 11. Anysuitable arrangement of switches can be used.

Turning to FIG. 3a, the engagement of two portions of row 13 conductivefabric is shown in which the interwoven sets of fibers 24 and 25 areshown in engagement at a plurality of points. The conductive fabricprovides a plurality of electrical contacts to assure the completion ofthe electrical circuit when the deflection layer 6 is operated to movethe upper fabric 5 down into engagement with layer fabric 3.

An alternative embodiment of the invention is shown in FIGS. 5 and 6having three layers of conductive fabric including the additionalintermediate layer 26 and additional separator layer 4a. As shown inFIG. 6, deflection lips 19 and 19a operate in the same manner as theswitch described above except that after initial engagement of the upperfabric and intermediate fabric they continue their movement downwardinto engagement with the lower fabric layer to complete a three-elementswitch.

The switch of this invention is also useful in responding to pressureapplied by liquid pressure, for example, the depth of a liquid could besensed by the pressure required to close the switch.

An array of switches may be used to record the information on a checkoffsheet where an audible signal tells the operator that each check markhas been effective to close a switch and in which scanning of all switchpoints to register the closed switches can be accomplished by using theelectronic keyboard art techniques.

I claim:

1. An electrical switch which is closed by the application of pressureagainst an area of the switch and is opened when the pressure is removedcomprising a. an electrically nonconductive base;

b. a first electrically conductive layer positioned against such base;

c. a nonconductive separator means placed against the side of theconductive layer opposite the base, said separator means having anopening therein;

d. a second electrically conductive layer placed against the side of theseparator means opposite the rst conductive layer;

e. a layer of nonconductive noncompressible material placed against theside of the second electrically conductive layer opposite thenonconductive layer means, said noncompressible layer having anelongated opening positioned adjacent the opening in the separatormeans; and

f. a pressure-responsive deectable portion of the noncompressible layerpositioned adjacent the opening capable of being deflected down intosaid opening whereby the application of pressure transmitted to andagainst the pressure-responsive deflectable portion causes said portionto move a portion of the second conductive layer against the firstconductive layer to close the switch.

2. The switch of claim 1 in which the conductive layers are fabricshaving electrically conductive material coated thereon.

3. The switch of claim 1 in which the pressure-responsive deflectableportion of the noncompressible layer includes a plurality of lip meansadjacent an elongated opening in said noncompressible layer which lipmeans are capable of being deflected down into said opening in theseparator means.

4. The switch of claim 1 having a sheet positioned in engagement withthe noncompressible layers for receiving applied pressure which is inturn transmitted to said noncompressible layer.

5. An array of pressure-operated electrical switches arranged in a unitcomprising a. an electrically nonconductive baseplate forming the baseof the switches,

b. a fabric layer positioned on the baseplate and having electricallyconductive portions,

c. a nonconductive separator layer placed against the side of the fabricopposite the plate, said separator having a plurality of openingstherein,

d. a second fabric layer having electrically conductive portions andelectrically nonconductive portions positioned on the separator layer,and

e. a nonconductive noncompressible dellection sheet placed on the secondlayer, said sheet having deectable portions in alignment with saidopenings in the separator layer to permit the deectable portions to bedellected against the second layer of fabric, said layer having slitstherein.

6. The array of claim 5 in having in addition a protective sheetpositioned on the noncompressible deflection sheet on which pressure isdirectly applied.

7. The array of claim 5 in which layers having conductive andnonconductive portions are nylon fabric in which the conductive portionsincludes woven fibers coated with silver metal.

8. The switch of claim 1 in which the base and the first electricallyconductive layer comprise a nonconductive sheet materail having selectedareas of conductive material adhered to the sheet material.

9. The array of claim 5 in which the base and the rst electricallyconductive layer comprise a nonconductive sheet material having selectedareas of conductive materail adhered to the sheet material.

10. The array of claim 5 having positioned thereon a sheet of materialhaving delineated areas which indicate where pressure may be electivelyapplied.

1l. An array of claim 5 capable of responding to the application ofpressure of a writing instrument and having positioned thereon a sheetof material having delineated areas indicating where pressure may beelfectively applied by such instrument.

12. The array of claim 11 in which the sheet is capable of recordingmarks made by such instrument.

I3. The switch of claim l having positioned thereon a sheet of materialhaving delineated areas which indicate where pressure may be eectivelyapplied.

14. The switch of claim 1 capable of responding to the application ofpressure of a writing instrument and having positioned thereon a sheetof material having delineated areas indicating where pressure may beeectively applied by such instrument.

15. The switch of claim I4 in which the sheet js capable of recordingmarks made by such instrument.

I6. An electrical switch which is closed by the application of pressureagainst an area of the switch and is opened when the pressure is removedcomprising:

a. electrically nonconductive base means;

b. first electrically conductive means on said base:

c. nonconductive separator means adjacent said first conductive means onthe side of said first conductive means opposite said base, saidseparator means having an opening therein.'

d. second electrically conductive means adjacent said separator means onthe side of said separator means opposite said first electricallyconductive means; and

e. nonconductive and substantially noncompressible deflector meansadjacent said second electrically conductive means on the side thereofopposite said separator means, said defiector means having an elongatedopening positioned adjacent said opening in said separator means, andsaid defector means having a pressure responsive deflectable portionaligned with said opening in said separator means for defiection intosaid opening to bring said first and second electrically conductivemeans into contact.

I 7. The switch of claim 1 wherein at least one of said first and secondelectrically conductive means includes areas of conductive material on anonconductive sheet.

18. The switch of claim I6 in which the pressure-responsive deflectableportion of the noncompressible layer includes a plurality of lip meansadjacent said elongated opening in said noncompressible layer, which lipmeans are capable of being deflected down into said opening in theseparator means.

19. The switch of claim I6 having a sheet positioned in engagement withthe noncompressible layers for receiving applied pressure which is inturn transmitted to said noncompressible layer.

20. The switch of claim I6 having positioned thereon a sheet of materialhaving delineated areas which indicate where pressure may be eectivelyapplied.

21. The switch of claim 16 capable of responding to the application ofpressure of a writing instrument and having positioned thereon a sheetof material having delineated areas indicating where pressure may beeectively applied by such instrument.

22. The switch of claim 21 in which the sheet is capable of recordingmarks made by such instrument.

23. An array of pressure operated electrical switches arranged in a unitcomprising:

a. electrically nonconductive base means forming a base for theswitches;

b. first electrically conductive means on said base;

c. nonconductive separator means adjacent said first electricallyconductive means on the side thereof opposite said base, said separatorhaving a plurality of openings therein in alignnment with portions ofsaid first conductor means;

d. second electrically conductive means adjacent said separator means,portions of said second electrically conductive means being inAalignment with said openings in said separator means.' and e.nonconductive and substantially noncompressible deflection meansadjacent said second electrically conductive means, said deflectionmeans having deflectable portions in alignment with said openings insaid separator means to permit the deflectable portions to beselectively deflected toward said base means to bring portions of saidfirst and second electrically conductive means into contact, saiddeflectable portions having slits therein.

24. The switch of claim 23 wherein at least one of said first and secondelectrically conductive means includes areas of conductive material on anonconductive sheet.

25. The array of claim 23 including protective means positioned adjacentsaid deflection means on which pressure is applied.

26. The array of claim 23 wherein said defiectable portions include aplurality of lip means adjacent said slits. said lips being capable ofdeflection into said aligned openings in said separator means.

27. The array of claim 23 having positioned thereon a sheet of materialhaving delineated areas which indicate where pressure may be eectivelyapplied.

28. An array of claim 23 capable of responding to the application ofpressure of a writing instrument and having positioned thereon a sheetof material having delineated areas indicating where pressure may beeectvely applied by such instrument.

29. The array of claim 28 in which the sheet is capable of recordingmarks made by such instrument.

References Cited The following references, cited by the Examiner, are ofrecord in the patented file of this patent or the original patent.

8 UNITED STATES PATENTS 3,056,005 9/1962 Larson 200-86 R 3,308,2533/1967 Krakinowski 20G-86 R OTHER REFERENCES Brook et al.: ProgrammingElastic Diaphram Switching Matrix by Small Balls," IBM Tech. Disc.Bull., v01. 10, No. ll, April 1968.

10 DAVID SMITH, JR., Primary Examiner U.S. Cl. X.R.

ZOO- 46, 159 B; 23S-61.1

